Probability
of Simple
Events
Probability of Simple Events
Objective:
Students will be able to find the probability of a
simple event.
Students will be able to understand the
distinction between simple events and
compound events.
Essential Question:
(1) How do I find the probability of a simple
event?
(2) How can I distinguish between a simple and
compound event?
Probability of Simple Events
Vocabulary:
 Outcome – one possible result of a probability.
 Sample Space – the list of possible outcomes
for a probability event.
 Random – outcomes that occur at random if
each outcome is equally likely to occur.
 Simple Event – a specific outcome or type of
outcome.
 Complementary Events – the events of one
outcome happening and that outcomes not
happening are complimentary; the sum of the
probabilities of complementary events is 1.
Probability of Simple Events
Real World Example:
Best Buy is having an IPOD giveaway.
They put all the IPOD Shuffles in a
bag. Customers may choose an IPOD
without looking at the color. Inside the
bag are 4 orange, 5 blue, 6 green, and
5 pink IPODS. If Maria chooses one
IPOD at random, what is the probability
she will choose an orange IPOD?
Probability of Simple Events
Real World Example:
Best Buy is having an IPOD giveaway.
They put all the IPOD Shuffles in a
bag. Customers may choose an IPOD
without looking at the color. Inside the
bag are 4 orange, 5 blue, 6 green, and
5 pink IPODS. If Maria chooses one
IPOD at random, what is the probability
she will choose an orange IPOD?
P(orange) = 4/20 = 2/10 = 1/5 or 20%
Probability of Simple Events
What is a PROBABILITY?
- Probability is the chance that some
event will happen
- It is the ratio of the number of
ways a certain event can occur to
the number of possible outcomes
Probability of Simple Events
What is a PROBABILITY?
P(event) =
number of favorable outcomes
number of possible outcomes
Examples that use Probability:
(1) Dice, (2) Spinners, (3) Coins, (4) Deck of
Cards, (5) Evens/Odds, (6) Alphabet, etc.
Probability of Simple Events
What is a PROBABILITY?
0%
25%
50%
75%
100%
0
¼ or .25
½ 0r .5
¾ or .75
1
Impossible
Not Very
Likely
Equally Likely
Somewhat
Likely
Certain
Probability of Simple Events
Example 1: Roll a dice.
What is the probability of rolling a 4?
# favorable outcomes
P(event) =
# possible outcomes
1
P(rolling a 4) =
6
The probability of rolling a 4 is 1 out of 6
Probability of Simple Events
Example 2: Roll a dice.
What is the probability of rolling an even
number?
#
favorable
outcomes
P(event) =
# possible outcomes
3
1
P(even #) =
=
6
2
The probability of rolling an even number is 3 out of 6 or .5
or 50%
Probability of Simple Events
Example 3: Spinners.
What is the probability of spinning green?
# favorable outcomes
P(event) =
# possible outcomes
1
1
P(green) =
=
4
4
The probability of spinning green is 1 out of 4 or .25 or
25%
Probability of Simple Events
Example 4: Flip a coin.
What is the probability of flipping a tail?
# favorable outcomes
P(event) =
# possible outcomes
1
1
P(tail) =
=
2
2
The probability of spinning green is 1 out of 2 or .5 or 50%
Probability of Simple Events
Example 5: Deck of Cards.
What is the probability of picking a heart?
P(heart) =
# favorable outcomes
=
13
=
# possible outcomes
52
The probability of picking a heart is
1 out of 4 or .25 or 25%
1
4
What is the probability of picking a non heart?
P(nonheart) =
# favorable outcomes
=
39
# possible outcomes
52
The probability of picking a heart is
3 out of 4 or .75 or 75%
=
3
4
Probability of Simple Events
Key Concepts:
- Probability is the chance that some
event will happen
- It is the ratio of the number of
ways a certain even can occur to
the total number of possible
outcomes
Probability of Simple Events
Guided Practice:
Calculate the probability
of each independent event.
1) P(black) =
2) P(1) =
3) P(odd) =
4) P(prime) =
Probability of Simple Events
Guided Practice:
Answers.
1) P(black) = 4/8
2) P(1) = 1/8
1
3) P(odd) = /2
1
4) P(prime) = /2
Probability of Simple Events
Independent Practice:
Calculate the
probability of each independent event.
1) P(red) =
2) P(2) =
3) P(not red) =
4) P(even) =
Probability of Simple Events
Independent Practice:
1) P(red) = 1/2
2) P(2) = 1/4
1
3) P(not red) = /2
1
4) P(even) = /2
Answers.
Probability of Simple Events
Real World Example:
A
computer company manufactures 2,500
computers each day. An average of 100 of
these computers are returned with defects.
What is the probability that the computer
you purchased is not defective?
P(not defective) =
# not defective
total # manufactured
= 2,400 = 24
2,500 25
Probability of Simple Events
Thank You !!